During operation of an internal combustion engine combustion, a small amount of unburned fuel-air mixture is leaked to a crankcase through a gap between a cylinder wall and a piston. The leaked fuel-air mixture is called blow-by gas of the engine. The gases in the crankcase include unburned fuel gas, steam, and exhaust gas. The current technologies use positive crankcase ventilation (PCV) to route the blow-by gas to an intake manifold of the engine to utilize the fuel efficiently, minimize the discharge of the air pollutants, and solve the issue of the engine oil degradation.
US2014/0326226A1 discloses a PCV device adjacent to an exhaust gas recirculation (EGR) pipe to heat the blow-by gas and includes a plural of pipes inside the intake manifold to route the engine blow-by gas into a plurality of runners of the intake manifold.
With the development of automobile technology, variable displacement engines (VDE) have been applied in the vehicles. During an engine operation, some cylinders may be stopped to enhance the engine's efficiency in certain operation loads (e.g., a low operation load). Cylinder deactivation may be achieved by closing the cylinder's intake valve and exhaust valve. During cylinder deactivation, however, the blow-by gas may still route to every intake manifold branch (e.g., the PCV device in US2014/0326226A1) as in a normal cylinder operation, which may result in a low efficiency of the blow-by gas utilization and fluctuation of the fuel/air ratio, causing unstable combustion that effects smooth power output from the engine.